<template>
  <div class="container">
    <ul class="example-list">
      <li class="example-item" @click="show">
        <span class="open">{{ selectedText }}</span>
      </li>
    </ul>
    <transition name="picker-fade">
      <div
        class="picker"
        v-show="state === 1"
        @touchmove.prevent
        @click="_cancel"
      >
        <transition name="picker-move">
          <div class="picker-panel" v-show="state === 1" @click.stop>
            <div class="picker-choose border-bottom-1px">
              <span class="cancel" @click="_cancel">Cancel</span>
              <span class="confirm" @click="_confirm">Confirm</span>
              <h1 class="picker-title">Title</h1>
            </div>
            <div class="picker-content">
              <div class="mask-top border-bottom-1px"></div>
              <div class="mask-bottom border-top-1px"></div>
              <div class="wheel-wrapper" ref="wheelWrapper">
                <div class="wheel">
                  <ul class="wheel-scroll">
                    <li
                      v-for="(item, index) in pickerData"
                      :key="index"
                      :class="{ 'wheel-disabled-item': item.disabled }"
                      class="wheel-item"
                    >
                      {{ item.text }}
                    </li>
                  </ul>
                </div>
              </div>
            </div>
            <div class="picker-footer"></div>
          </div>
        </transition>
      </div>
    </transition>
  </div>
</template>

<script type="text/ecmascript-6">
import BScroll from "@better-scroll/core";
import Wheel from "@better-scroll/wheel";
BScroll.use(Wheel);

const STATE_HIDE = 0;
const STATE_SHOW = 1;

const COMPONENT_NAME = "picker";
const EVENT_SELECT = "select";
const EVENT_CANCEL = "cancel";
const EVENT_CHANGE = "change";
const WHEEL_INDEX_CHANGED = "wheelIndexChanged";

const DATA = [
  {
    text: "Venomancer",
    value: 1,
    disabled: "wheel-disabled-item",
  },
  {
    text: "Nerubian Weaver",
    value: 2,
  },
  {
    text: "Spectre",
    value: 3,
  },
  {
    text: "Juggernaut",
    value: 4,
  },
  {
    text: "Karl",
    value: 5,
  },
  {
    text: "Zeus",
    value: 6,
  },
  {
    text: "Witch Doctor",
    value: 7,
  },
  {
    text: "Lich",
    value: 8,
  },
  {
    text: "Oracle",
    value: 9,
  },
  {
    text: "Earthshaker",
    value: 10,
  },
];

export default {
  name: COMPONENT_NAME,
  data() {
    return {
      state: STATE_HIDE,
      selectedIndex: 2,
      selectedText: "open",
      pickerData: DATA,
    };
  },
  methods: {
    _confirm() {
      /*
       * if bs is scrolling, force it stop at the nearest wheel-item
       * or you can use 'restorePosition' method as the below
       */
      this.wheel.stop();
      /*
       * if bs is scrolling, restore it to the start position
       * it is same with iOS picker and web Select element implementation
       * supported at v2.1.0
       */
      // this.wheel.restorePosition()
      this.hide();
      const currentSelectedIndex = (this.selectedIndex =
        this.wheel.getSelectedIndex());
      this.selectedText = `${this.pickerData[currentSelectedIndex].text}-${currentSelectedIndex}`;
      this.$emit(EVENT_SELECT, currentSelectedIndex);
    },
    _cancel() {
      /*
       * if bs is scrolling, restore it to the start position
       * it is same with iOS picker and web Select element implementation
       * supported at v2.1.0
       */
      this.wheel.restorePosition();
      this.hide();
      this.$emit(EVENT_CANCEL);
    },
    show() {
      if (this.state === STATE_SHOW) {
        return;
      }
      this.state = STATE_SHOW;
      if (!this.wheel) {
        // waiting for DOM rendered
        this.$nextTick(() => {
          const wrapper = this.$refs.wheelWrapper.children[0];
          this._createWheel(wrapper);
        });
      }
    },
    hide() {
      this.state = STATE_HIDE;
    },
    _createWheel(wheelWrapper) {
      if (!this.wheel) {
        this.wheel = new BScroll(wheelWrapper, {
          wheel: {
            selectedIndex: this.selectedIndex,
            wheelWrapperClass: "wheel-scroll",
            wheelItemClass: "wheel-item",
            wheelDisabledItemClass: "wheel-disabled-item",
          },
          useTransition: false,
          probeType: 3,
        });
        // < v2.1.0
        this.wheel.on("scrollEnd", () => {
          this.$emit(EVENT_CHANGE, this.wheel.getSelectedIndex());
        });
        // v2.1.0, only when selectedIndex changed
        this.wheel.on(WHEEL_INDEX_CHANGED, (index) => {
          console.log(index);
        });
      } else {
        this.wheel.refresh();
      }
      return this.wheel;
    },
  },
};
</script>
<style lang="scss" scoped>
.example-list {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  margin: 80px 20px 0 20px;
  .example-item {
    background-color: white;
    padding: 0.8rem;
    border: 1px solid rgba(0, 0, 0, 0.1);
    box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.1);
    text-align: center;
    margin-bottom: 1rem;
    flex: 1;

    &.placeholder {
      visibility: hidden;
      height: 0;
      margin: 0;
      padding: 0;
    }
  }
}

.picker {
  position: fixed;
  left: 0;
  top: 0;
  z-index: 100;
  width: 100%;
  height: 100%;
  overflow: hidden;
  text-align: center;
  font-size: 14px;
  background-color: rgba(37, 38, 45, 0.4);

  &.picker-fade-enter,
  &.picker-fade-leave-active {
    opacity: 0;
  }

  &.picker-fade-enter-active,
  &.picker-fade-leave-active {
    transition: all 0.3s ease-in-out;
  }

  .picker-panel {
    position: absolute;
    z-index: 600;
    bottom: 0;
    width: 100%;
    height: 273px;
    background: white;

    &.picker-move-enter,
    &.picker-move-leave-active {
      transform: translate3d(0, 273px, 0);
    }

    &.picker-move-enter-active,
    &.picker-move-leave-active {
      transition: all 0.3s ease-in-out;
    }

    .picker-choose {
      position: relative;
      height: 60px;
      color: #999;

      .picker-title {
        margin: 0;
        line-height: 60px;
        font-weight: normal;
        text-align: center;
        font-size: 18px;
        color: #333;
      }

      .confirm,
      .cancel {
        position: absolute;
        top: 6px;
        padding: 16px;
        font-size: 14px;
      }

      .confirm {
        right: 0;
        color: #007bff;

        &:active {
          color: #5aaaff;
        }
      }

      .cancel {
        left: 0;

        &:active {
          color: #c2c2c2;
        }
      }
    }

    .picker-content {
      position: relative;
      top: 20px;

      .mask-top,
      .mask-bottom {
        z-index: 10;
        width: 100%;
        height: 68px;
        pointer-events: none;
        transform: translateZ(0);
        position: absolute;
      }

      .mask-top {
        top: 0;
        background: linear-gradient(
          to top,
          rgba(255, 255, 255, 0.4),
          rgba(255, 255, 255, 0.8)
        );
      }

      .mask-bottom {
        bottom: 1px;
        background: linear-gradient(
          to bottom,
          rgba(255, 255, 255, 0.4),
          rgba(255, 255, 255, 0.8)
        );
      }

      .wheel-wrapper {
        display: flex;
        padding: 0 16px;

        .wheel {
          flex: 1;
          width: 1%;
          height: 173px;
          overflow: hidden;
          font-size: 18px;

          .wheel-scroll {
            padding: 0;
            margin-top: 68px;
            line-height: 36px;
            .wheel-item {
              height: 36px;
              overflow: hidden;
              white-space: nowrap;
              color: #333;

              &.wheel-disabled-item {
                opacity: 0.2;
              }
            }
          }
        }
      }
    }

    .picker-footer {
      height: 20px;
    }
  }
}
</style>
